Resolution and sensitive detection of carboxylic acid enantiomers using fluorescent chiral derivatization reagents by high-performance liquid chromatography

Resolution of chiral drugs by liquid chromatography based upon diastereomer formation with chiral derivatization reagents

Chiral derivatization reagents for resolution of biologically important compounds, such as chiral drugs by high-performance liquid chromatography (HPLC), based upon pre-column derivatization and diastereomer formation, are reviewed. The derivatization reagents for various functional groups, i.e., amine, carboxyl, carbonyl, hydroxyl and thiol, are evaluated in terms of reactivity, stability, wavelength, handling, versatility, sensitivity, and selectivity. The applicability of the reagents to the analyses of drugs and bioactive compounds are included in the text.

Chiral separation of pharmaceuticals possessing a carboxy moiety

The separation of carboxylic enantiomers in the pharmaceutical field using high-performance liquid chromatographic and capillary electrophoretic techniques is reviewed. The techniques used for chiral separation include diastereomer derivatization, a chiral mobile phase, a chiral stationary phase (high-performance liquid chromatography) and chiral additives (capillary electrophoresis). Practical and conventional separation systems for pharmaceutical applications, such as pharmacokinetics, optical purity testing and stability studies, are described. A comprehensive collection of applications to carboxylic drugs and other carboxylic compounds of pharmaceutical interest is listed in the tables. The characteristics of each enantioseparation method are also discussed briefly.

Methylated Nepsilon-dansyl-L-lysine as a fluorogenic reagent for the chiral separation of carboxylic acids

Dansyl amino acids having a free amino group and an asymmetric carbon atom were examined as a labeling reagent for chiral compounds containing carboxylic moieties to realize enantiomeric separation as well as fluorimetric determination. We tested dansyllysine by reacting it with (+)- and (-)-ibuprofen as a model carboxylic enantiomer. As the intramolecular carboxylic moiety of the dansyl amino acid interfered in the condensation reaction to form an amide bond with the carboxylic acid, the moiety was masked by methylation with trimethylsilyldiazomethane before the reaction. These derivatives were reacted with (+)- and (-)-ibuprofen and better enantiomeric resolution was achieved with methylated dansyllysine on a reversed-phase column. The derivatisation reaction was facilitated by the use of catalysts that are commonly employed in peptides synthesis. The reaction was completed within 5 min at room temperature when diethyl phosphorocyanidate was used. Due to the dansyl moiety, methylated dansyl-lysine enables a sensitive determination of ibuprofen with a fluorescence detector, in addition to the capability of enantiomer resolution. In tests, the detection limits for (+) and (-)-ibuprofen were 4 pmol per injection (S/N=3) at an excitation wavelength of 340 nm and an emission wavelength of 523 nm. Linear responses for the determination of (+) and (-)-ibuprofen in human urine were also demonstrated (r > or = 0.998) in the range from 10 to 1000 ng/ml. The precision and accuracy for urine samples spiked with (+)- and (-)-ibuprofen at 10, 100 and 1000 ng/ml were <10.1 and <14.6% (n=4), respectively.

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidine (DNS-Apy) as a fluorescence chiral labelling reagent for carboxylic acid enantiomers

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidi ne (DNS-Apy) has been synthesized for the separation of carboxylic acid enantiomers by high-performance liquid chromatography (HPLC) and sensitive detection. The reagent reacts with carboxylic acids at room temperature in the presence of activation agents 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP). The maximum emission of the diastereomeric amide derived from (S)-phenylpropionic acid and ketoprofen derivatives of DNS-Apy was at 530 nm with excitation at 340 nm. The emission wavelength shifted towards the blue and the fluorescence intensities increased with increasing acetonitrile concentration in the medium. The diastereomers derived from anti-inflammatory drugs were efficiently resolved with a reverse-phase column using water:acetonitrile mixture as mobile phase. All of the racemate of arylpropionic acid derivatives gave equal fluorescence intensity of the two enantiomers with the exception of ketoprofen derivatives where the intensity of the first eluting enantiomer was half that of the second.

Methods of analysis of chiral non-steroidal anti-inflammatory drugs

Although the analysis of the enantiomers of chiral non-steroidal anti-inflammatory drugs (NSAIDs) has been carried out for over 20 years, there often remains a deficit within the pharmaceutical and medical sciences to address this issue. Hence, despite world-wide therapeutic use of chiral NSAIDs the importance of stereoselectivity in pharmacokinetic, pharmacodynamic and pharmacological activity and disposition has often been ignored. This review presents both the general principles that allow separation of chiral NSAID enantiomers, and discusses both the advantages and disadvantages of the available chromatographic assay methods and procedures used to separately quantify NSAID enantiomers in biological matrices.

Recent progress in liquid chromatographic enantioseparation based upon diastereomer formation with fluorescent chiral derivatization reagents

Techniques for the resolution by liquid chromatography of racemic compounds based upon diastereomer formation with a fluorescent chiral reagent are outlined in this review. The tagging reagents for various functional groups, i.e. amine, carboxyl, hydroxyl and thiol, are evaluated in terms of optical purity, handling, flexibility, stability, sensitivity and selectivity. The applicabilities of the reagents to drugs and biologically important substances are included in the text. This review is limited to reagents with fluorophores and reagents that exhibit fluorescence.